Use of substituted 2-(2-hydroxyaryl)-2H-benzotriazolesulfonates as photostabilizing agents for natural synthetic fibres

ABSTRACT

A method for protecting synthetic and natural fibres against phototendering. The method comprises treating the fibres with a substituted benzotriazolesulfonate of the following formula: ##STR1## wherein (I) R 1  is hydrogen or halogen, R 2  is hydrogen or alkyl, R 3  is hydrogen or hydroxy, R 4  is --SO 3  X where X is hydrogen or an alkali metal, and R 5  is hydrogen, with the proviso that R 2  is not methyl when R 1  and R 3  are hydrogen; or 
     (II) R 1 , R 3  and R 4  are hydrogen, R 2  is --SO 3  X where X is hydrogen or an alkali metal, and R 5  is --OR 6  where R 6  is hydrogen or alkyl; or 
     (III) R 1  is hydrogen or halogen, R 2  is --SO 3  X where X is hydrogen or an alkali metal, R 3  and R 5  are hydrogen, and R 4  is hydrogen, alkyl or benzyl; or 
     (IV) R 1  is --SO 3  X where X is hydrogen or an alkali metal, R 2  is alkyl, R 3  and R 5  are hydrogen, and R 4  is hydrogen or alkyl; 
     under acidic conditions. The method is particularly suitable for treating wool, silk and nylon fibres, including blends thereof.

This invention relates to a method for protecting synthetic and naturalfibres against phototendering by the use of substituted2-(2'-hydroxyaryl)-2H-benzotriazolesulfonates.

Phototendering is a light-induced phenomenon which manifests itself as aloss in strength and abrasion resistance of the fibre. The resultantdamage is particularly noticeable in woollen car upholstery and inwoollen curtains of the scrim variety, which sometimes fall apart withina few years upon exposure to sunlight--even through glass. It is ofcourse well known that synthetic fibres and plastics are also damaged bylight and it has become commonplace for additives to be added to thepolymeric material before fabrication in the hope of retarding suchlight-induced damage. Particularly effective additives are certainorganic compounds, known as ultraviolet absorbers, which absorbultraviolet radiation preferentially thereby protecting the fibre orplastic from the damaging effects of sunlight.

The present invention had its origin in the notion that suitablymodified ultraviolet absorbers might protect natural protein andsynthetic fibres against photodegradation, particularly phototendering.Particularly relevant to the present invention was the observation thatcertain sulfonic acid derivatives of substituted2-(2'-hydroxyphenyl)-2H-benzotriazoles, a well-known class ofultraviolet absorber, reduced the rate of photoyellowing of bleachedwool [Waters and Evans, Text. Res. J., 48, 251-255, (1978)].Accordingly, a wide variety of benzotriazolesulfonic acids wassynthesized and applied to certain natural and synthetic fibresparticularly wool, silk and nylon; their effectiveness in reducingphotodegradation is the subject of this invention.

The essential structural feature of2-(2'-hydroxyphenyl)-2H-benzotriazole photostabilizers is the phenolichydroxyl group, which is capable of forming both intra- andinter-molecular hydrogen bonds. It is the intramolecularlyhydrogen-bonded form (Ia) which is responsible for the photoprotective(or photo-stabilizing) effect; if the proportion of the ##STR2##intermolecularly hydrogen-bonded form (Ib) is increased, as can happenin solvents [Heller, Eur. Poly. J., Supplement (1969), 105-132] orpolymeric substrates [cf. Leaver, J. Polym. Sci. (Polym. Chem. Ed.)(1982), 20, 2429] capable of disrupting the intramolecular hydrogenbond, then the photostabilizing efficiency is reduced. On the otherhand, if the phenolic hydroxyl group is flanked by a bulky substituent(e.g., t-alkyl) located in the ortho position (i.e., at R), then theintramolecular hydrogen bond may be protected to some extent from thedisrupting effect of hydrogen bond breaking solvents [see also Heller(reference cited above)]. Particular attention has been paid to this(possibly beneficial) bulky group effect in the research which is thesubject of the present application.

There are prior reports of the use of unsulfonated2-(2'-hydroxyphenyl)-2H-benzotriazoles for the protection, with varyingdegrees of success, of some natural fibres against light e.g., mohair[van Rensburg, SAWTRI Bull., 12(4), 48-53 (1978)], cotton [van Rensburg,SAWTRI Technical Report No. 309 (1979)] and silk [e.g., Kuwahra,Nakamichi and Shoji, Nippon Sanshigaku Zasshi, 46(6), 486-492 (1977)].Of particular relevance to the present invention, is the use ofsulfonated 2-(2'-hydroxyphenyl)-2H-benzotriazoles for the protection ofwool against yellowing [Waters and Evans, Text. Res. J., 48(5), 251-255(1978); Leaver, Waters and Evans, J. Poly. Sci. (Poly. Chem. Ed.), 17,1531-1541 (1979)].

The synthesis of substituted sodium2-(2'-hydroxyphenyl)-2H-benzotriazolesulfonates has been claimed inseveral recent patents (collected below). However data concerning thespecific use of these sulfonates is lacking; in particular, noprotection of wool, wool-blends or synthetic fibres against sunlight isdisclosed. The following relevant patents are recorded:

Japanese Pat. No. 7,510,623; Apr. 23, 1975 (Toyobo Co Ltd)

U.S. Pat. No. 3,849,373; Nov. 19, 1974 (Du Pont de Nemours)

Swiss Pat. No. 615,165; Jan. 15, 1980 (Ciba-Geigy)

Swiss Pat. No. 615,167; Jan. 15, 1980 (Ciba-Geigy)

Ger. Pat. No. 2,835,846; Feb. 22, 1979 (Ciba-Geigy)

Ger. Pat. No. 2,835,529; Mar. 01, 1979 (Ciba-Geigy)

U.S. Pat. No. 4,141,903; Feb. 27, 1979 (Ciba-Geigy)

It is therefore an object of the present invention to provide means toprotect synthetic and natural fibres such as wool, silk and nylon fromphotodegradation. The extension of this invention to dyed fibres is alsointended.

According to the present invention there is provided a method forprotecting synthetic and natural fibres against photodegradation whichcomprises treating the fibres with a substituted benzotriazolesulfonateof the following formula: ##STR3## wherein (I) R₁ is hydrogen orhalogen, R₂ is hydrogen or alkyl, R₃ is hydrogen or hydroxy, R₄ is --SO₃X where X is hydrogen or an alkali metal, and R₅ is hydrogen, with theproviso that R₂ is not methyl when R₁ and R₃ are hydrogen; or

(II) R₁, R₃ and R₄ are hydrogen, R₂ is --SO₃ X where X is hydrogen or analkali metal, and R₅ is --OR₆ where R₆ is hydrogen or alkyl; or

(III) R₁ is hydrogen or halogen, R₂ is --SO₃ X where X is hydrogen or analkali metal, R₃ and R₅ are hydrogen, and R₄ is hydrogen, alkyl orbenzyl; or

(IV) R₁ is --SO₃ X where X is hydrogen or an alkali metal, R₂ is alkyl,R₃ and R₅ are hydrogen, and R₄ is hydrogen or alkyl;

under acidic conditions.

Preferred alkyl groups include methyl, ethyl, propyl (n and i), butyl (sand t), t-amyl and t-octyl. Preferred halogen is chlorine and preferredalkali metal is sodium.

Fibres found to be particularly amenable to the process are wool(including dyed wool), silk and nylon fibres, and blends thereof.

Preferred embodiments of the invention will now be described withreference to the following examples which illustrate the extent ofphotodegradation in wool, silk and nylon samples treated with thebenzotriazolesulfonates according to the invention. The extent ofphoto-degradation was measured by the breaking load found for fabricstrips or yarns before and after irradiation. Unless otherwise stated inthe examples, the ultraviolet absorbers (5% o.w.f.) were normallyapplied to the fabric at 80° for 90 minutes from an aqueous dyebath(liquor:wool ratio=60:1) containing sulfuric acid (3% o.w.f.) and sodiumsulfate (5% o.w.f.) using an Ahiba laboratory dyeing machine.Exhaustions (as measured by optical density changes of the dyebaths)ranged from 60-100% (mainly 80-100%).

Treated and control fabric samples (30 cm×25 cm) were exposed for up to2000 hr at a distance of 20 cm from a mercury-tungsten-phosphor lamp(Philips MBTF or ML 500 W type), which is considered to provideirradiation similar to that of sunlight.

Breaking loads were determined in the weft direction on conditioned(20°; 65% r.h.) fabric strips (weft 125 mm and warp 40 mm; rate ofextension 125 mm/min). The results quoted are the means of sixmeasurements. The results are collected in eight Examples. Examples 1-7are concerned with wool [including dyed wool (see Example 7)], andExample 8 with nylon.

EXAMPLE 1

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT                                               ##STR4##                                                                                                 Strength (%)                                      Substituents                                                                             Breaking Load (lb)                                                                             remaining after                                   R.sub.1                                                                            R.sub.2                                                                              R.sub.3                                                                              Before  After 2000 hr                                                                          irradiation                               ______________________________________                                        Untreated  34.0       4.7       13.8                                          H    H      OH     34.3    14.2     41.4                                      H     .sub.-t-Oct                                                                         H      45.3    11.5     25.4                                      H     .sub.-t-Bu                                                                          H      37.8    19.0     50.3                                      Cl   Me     H      35.6    13.4     37.6                                      ______________________________________                                    

EXAMPLE 2

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT                                               ##STR5##                                                                                             Strength (%)                                                   Breaking Load (lb)                                                                           remaining after                                       Substituent R.sub.6                                                                      Before    After 2000 hr                                                                            irradiation                                   ______________________________________                                        Untreated  34.0       5.0       14.7                                          H          36.1      21.6       59.8                                          Me         35.9      21.8       60.7                                           -n-C.sub.12 H.sub.25                                                                    37.2      25.1       67.5                                          ______________________________________                                    

EXAMPLE 3

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT                                               ##STR6##                                                                                            Strength (%)                                                   Breaking Load (lb)                                                                           remaining after                                        R.sub.4 R.sub.1                                                                             Before    After 2000 hr                                                                          irradiation                                  ______________________________________                                        Untreated 33.3       9.1       27.3                                           H       H     36.3      16.8     46.3                                         Me      H     43.1      22.1     51.3                                         Et      H     36.1      15.1     41.8                                          -n-Pr  H     35.4      24.1     68.1                                          .sub.-i-Pr                                                                           H     33.7      24.7     73.3                                          .sub.-s-Bu                                                                           H     34.9      26.4     75.6                                         CH.sub.2 Ph                                                                           H     35.1      22.8     65.0                                         H       Cl    36.4      12.8     35.2                                         Me      Cl    35.9      16.6     46.2                                         ______________________________________                                    

EXAMPLE 4

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT                                               ##STR7##                                                                                            Strength (%)                                                   Breaking Load (lb)                                                                           remaining after                                        R.sub.4                                                                              R.sub.2                                                                              Before    After 2000 hr                                                                          irradiation                                  ______________________________________                                        Untreated 40.5       7.5       18.5                                           H      Me     41.7      21.7     52.0                                         Me     Me     41.7      27.0     64.7                                          .sub.-i-Pr                                                                           .sub.-t-Bu                                                                          38.0      29.8     78.4                                          .sub.-t-Bu                                                                          Me     41.6      35.6     85.6                                          .sub.-t-Am                                                                          Me     37.6      31.8     84.6                                         ______________________________________                                    

EXAMPLE 5

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT:                                             EFFECT OF APPLICATION pH                                                                           % Breaking Load                                          Sample        pH.sup.+                                                                             Remaining after 2000 hr                                  ______________________________________                                        Untreated Wool                                                                              --     15.1                                                     Control +     2      15.5                                                     Absorber*     2      85.6                                                     Control +     4      12.6                                                     Absorber*     4      68.6                                                     Control +     5.5    12.1                                                     Absorber*     5.5    53.5                                                     ______________________________________                                         ##STR8##                                                                      .sup.+ Exhaustion of Absorber Data: pH 2 (93%); pH 4 (88%); pH 5.5 (76%).

EXAMPLE 6

    ______________________________________                                        PROTECTION OF WOOL AGAINST LIGHT:                                             EFFECT OF ABSORBER CONCENTRATION                                              Absorber*        % Breaking Load                                              Concentration (% o.w.f.)                                                                       Remaining after 2000 hr                                      ______________________________________                                        0                10.3                                                         0.6              28.9                                                         1.2              44.5                                                         3.1              61.9                                                         5.0              77.4                                                         ______________________________________                                         *Applied at pH2; for Formula, see Example 5.                             

EXAMPLE 8

    ______________________________________                                        PROTECTION OF SILK AND NYLON AGAINST LIGHT                                    Fabric     Treatment*                                                                              % Breaking Load Remaining                                ______________________________________                                        Silk.sup.+ None       4                                                                  Absorber  28                                                       Nylon 66.sup.++                                                                          None      16                                                                  Absorber  67                                                       ______________________________________                                         *Absorber (3% o.w.f. used): for Formula, see Example 5                        .sup.+ Irradiated for 500 HR at                                               .sup.++ Irradiated for 800 HR at 45°.                             

EXAMPLE 7

    ______________________________________                                        PROTECTION OF DYED WOOL AGAINST LIGHT                                                    After 1000 hr  After 600 hr                                        Treatment  at 45°  at 70°                                       (or Additive)                                                                            BL(% RET)* ΔE.sup.δ                                                                  BL(% RET)*                                                                             ΔE.sup.δ                   ______________________________________                                        None       29.8       8.6     19.1     21.8                                   Absorber.sup.+                                                                           67.3       1.2     55.6     10.9                                   Bordeaux Dye.sup.++                                                                      42.3       5.9     35.5     12.4                                   Bordeaux Dye &                                                                           60.4       4.1     50.2      6.7                                   Absorber                                                                      Green Dye.sup.++                                                                         40.5       14.3    32.3     15.6                                   Green Dye &                                                                              60.2       7.4     41.5      9.8                                   Absorber                                                                      Brown Dye.sup.++                                                                         45.8       5.2     35.7      8.6                                   Brown Dye &                                                                              67.9       2.0     52.7      4.3                                   Absorber                                                                      Yellow Dye.sup.++                                                                        41.4       10.5    30.2     11.8                                   Yellow Dye &                                                                             57.3       5.7     51.5      6.8                                   Absorber                                                                      Grey Dye.sup.++                                                                          37.3       6.8     29.4     10.3                                   Grey Dye & 53.1       3.9     49.8      6.2                                   Absorber                                                                      ______________________________________                                         *% Breaking Load Retained                                                     .sup.+ Absorber (2% o.w.f.) used: for Formula, see Example 5.                 .sup.++ Isolan (Bayer) Dyes used: Premetallized Azo Dyes (Lightfastness       ≧ 6) Applied at Standard Depth.                                        .sup.δ ΔE: Colour Difference Values, based on the CIE L,a,b       colour scheme (A measure of dye fading).                                 

The ultraviolet absorbers shown in Examples 1-3 were prepared via directsulfonation (with chlorosulfonic acid) of the parent benzotriazolederivatives (a typical preparation is described below).

The sulfonates shown in Example 4 where prepared by the reduction (withsodium dithionite) of the corresponding sodiumo-nitrophenylazobenzenesulfonates (a typical preparation is describedbelow).

In the first four examples, the first two columns of data show thebreaking loads before and after irradiation; the third column shows thepercentage strength remaining in the fabric after irradiation (thisparameter was derived directly from the data shown in the first twocolumns). An assessment of the data collected in the examples leads tothe following general conclusions:

(i) All the sodium benzotriazolesulfonates studied protect wool againstphotodegradation. The degree of protection afforded increases as thepercentage of sulfonate o.w.f. is increased (see Example 6).

(ii) The location of the sulfonic acid group in the molecule affects thedegree of protection, protection being less when the sulfonic acid groupis adjacent to the hydrogen bonded phenolic group (see Example 1) thanwhen it is located elsewhere (see Examples 2-4).

(iii) The pH at which the benzotriazolesulfonate is applied has aneffect on its subsequent protective affect (see Example 5).

(iv) Incorporation of a long chain alkyl group into the moleculeincreases the degree of photoprotection (see Example 2).

(v) Incorporation of a bulky alkyl or aralkyl group (specifically t-Bu,i-Pr, s-Bu, t-Am or benzyl) into the molecule ortho to the hydrogenbonded OH group increases dramatically the degree of protection obtained(see Examples 3 and 4). This result confirms the original hypothesisthat such ortho-located bulky groups would have a beneficial effect onthe degree of protection afforded by2-(2'-hydroxyaryl)-2H-benzotriazolesulfonates.

(vi) The invention is particularly useful for dyed wool (see Example 7),the dyes [Isolans (Bayer)] being premetallised azo dyes of the sortfrequently used in car upholstery. It will be seen that dyed fabricstreated with a t-butyl-benzotriazolesulfonate are protected not onlyagainst phototendering (B.L. column) but also, to some extent, againstdye photofading (ΔE column). In addition to irradiation at 45° (for 1000h), comparisons were also made for irradiations at 70° C. (for 600 hr),conditions under which the fabric temperature exceeds 80° C. Such atemperature is likely to be experienced by the sunlight-irradiatedupholstery fabric of a car during a warm summer's day.

(vii) A further study (see Example 8) showed that both silk (absorberapplied at pH 2) and delustred nylon 66 (absorber applied at pH 4) wereprotected against phototendering by the t-butyl-benzotriazolesulfonate.

PREPARATION OF SODIUM 2-(2'-Hydroxyaryl)-2H-Benzotriazolesulfonates (i)Preparation of sodium3-(2'H-benzotriazol-2'-yl)-5-t-butyl-2-hydroxybenzenesulfonate ##STR9##

This procedure was used for all the sulfonates shown in Examples 1-3.When chlorosulfonic acid (2.20 g; 19 mmol) was added dropwise to a warm(60°) stirred solution of 2-(2'H-benzotriazol-2'-yl)-4-t-butylphenol(5.0 g; 19 mmol) in chlorobenzene (50 ml), a precipitate (the startingbenzotriazole) was formed. However, when the temperature of the mixturewas raised to the boiling point, this precipitate dissolved and, afterabout 10 min, a fresh precipitate (the sulfonic acid) was formed. Afterboiling under reflux for 2 hr, the mixture was cooled, and theprecipitate filtered and washed several times with hexane. This solidwas dissolved in water and the solution filtered to remove someamorphous material. The filtrate was then brought to pH 7 by theaddition of 10% sodium carbonate solution, and the resultant precipitate(the title sodium salt) (3.08 g) filtered, washed with ice-cold waterand dried. Recrystallization from boiling water gave colourless needles.'H n.m.r. (dimethyl sulfoxide-d₆): δ1.33, s, t-Bu; 7.65, d(Jc. 2 Hz), H4or H6; 7.80, d(Jc. 2 Hz), H6 or H4; 11.03, s, OH. The benzotriazole ringprotons were revealed as an AA'BB' pattern centred at δ7.80. The productabsorbed in water at 297 and 330 nm.

(ii) Preparation of sodium2-(3'-t-amyl-2'-hydroxy-5'-methyl)phenyl-5-(2H)-benzotriazolesulfonate##STR10##

This procedure was used for the sulfonates shown in Example 4. Thestarting dye was prepared by coupling 4-amino-3-nitrobenzene-sulfonicacid with 2-t-amyl-4-methylphenol under acidic conditions [cf. Rody etal (Ciba-Geigy), Ger. Pat., 2,334,770 (Mar. 14, 1974); Rosevear andWilshire, Aust. J. Chem., 35, 2089, 1982]. The resultant dye wasisolated by bringing the pH of the mixture to 7 with 1N hydrochloricacid and then adding salt. Some residual stickiness (due to the presenceof unreacted phenol) was removed by suspending the dye in boiling hexanefor 15 min. To a stirred hot (steam bath) solution of the dye (2.78 g;c. 7 mmol) in 4N sodium hydroxide (24 ml) was added dropwise a solutionof sodium dithionite (not less than 85% pure) (6.3 g; 28 mmol) in water(24 ml). The initial deep purple colour of the solution was slowlyreplaced by an orange-yellow colour. After 3 hr on the steam bath, thesolution was filtered hot and the title sodium salt (1.38 g)crystallized from the filtrate as pale yellow crystals. 'H n.m.r.(dimethyl sulfoxide-d₆): δ0.67, t(Jc. 7 Hz), CH₂ CH₃ 1.42, s, C(CH₃)₂ ;1.97, q(Jc. 7 Hz), CH₂ CH₃ ; 2.37, s, Ar CH₃ ; 7.17, d(Jc. 2 Hz), H4';7.90, d(Jc. 2 Hz), H6'; 11.20, vb, OH. The remaining signals could notbe assigned. The product absorbed in water at 305 and 348 (inflexion)nm.

We claim:
 1. A method for protecting natural fibres againstphototendering which comprises treating the fibres with a substitutedbenzotriazolesulfonate of the following formula: ##STR11## wherein R₁ is--SO₃ X where X is hydrogen or an alkali metal, R₂ is alkyl, R₃ and R₅are hydrogen, and R₄ is hydrogen or alkyl; under acidic conditions.
 2. Amethod as defined in claim 1, which is carried out at a pH within therange of 2.0-5.5 with sulphuric acid.
 3. A method as defined in claim 1,in which the fibres are treated ith the substitutedbenzotriazolesulfonate for about 90 minutes at about 80° C.
 4. A methodas defined in claim 1, in which the liquor:fibre ratio is about 60:1. 5.A method as defined in claim 1, in which the fibre is wool includingdyed wool, or silk, or blends thereof.
 6. A method as defined in claim1, in which, in the formula of the substituted benzotriazolesulfonate,the halogen is chlorine, the alkali metal is sodium, and the alkyl ismethyl, ethyl, propyl (n and i) butyl (s and t), or t-amyl.
 7. A methodas defined in claim 1, in which the substituted benzotriazolesulfonateis selected from the group consisting of:sodium2-(3'-t-amyl-2'-hydroxy-5'-methyl)phenyl-5-(2H)-benzotriazolesulfonate;and sodium2-(3'-i-propyl-2'-hydroxy-5'-t-butyl)phenyl-5-(2H)-benzotriazolesulfonate.8. A method as defined in claim 1 in which the substitutedbenzotriazolesulfonate is sodium,2-(3'-t-butyl-2'-hydroxy-5'-methyl)phenyl-5-(2H)-benzotriazolesulfonate.9. A natural fibre which has been treated against phototendering with anagent which comprises a substituted benzotriazolenesulfonate of thefollowing formula: ##STR12## wherein R₁ is --SO₃ X where X is hydrogenor an alkali metal, R₂ is alkyl, R₃ and R₅ are hydrogen, and R₄ ishydrogen or alkyl; under acidic conditions.